Since the invention of the integrated circuit (IC), the semiconductor industry has experienced continued rapid growth due to continuous improvements in the integration density of various electronic components (e.g., transistors, diodes, resistors, capacitors, etc.). For the most part, this improvement in integration density has come from repeated reductions in minimum feature size, which allows more components to be integrated into a given area.
These integration improvements are essentially two-dimensional (2D) in nature, in that the volume occupied by the integrated components is essentially on the surface of the semiconductor wafer. Although dramatic improvement in lithography has resulted in considerable improvement in 2D integrated circuit formation, there are physical limits to the density that can be achieved in two dimensions. One of these limits is the minimum size needed to make these components. Also, when more devices are put into one chip, more complex designs are required.
In an attempt to further increase circuit density, three-dimensional (3D) integrated circuits have been investigated. In a typical formation process of a 3D IC, two dies are bonded together and electrical connections are formed between each die and contact pads on a substrate. For example, one attempt involved bonding two dies on top of each other. The stacked dies were then bonded to a carrier substrate and wire bonds electrically coupled contact pads on each die to contact pads on the carrier substrate. This attempt, however, requires a carrier substrate larger than the dies for the wire bonding.
More recent attempts have focused on through-silicon vias (TSVs). Generally, TSVs are formed by etching a vertical via through a substrate and filling the via with a conductive material, such as copper. The TSVs may be used to provide an electrical contact on a backside of the semiconductor substrate to semiconductor circuitry on an opposing side of the substrate, or to provide an electrical contact to semiconductor circuitry on a stacked die. In this manner, dies may be stacked while maintaining a smaller package size.
Generally, the process used to form a TSV involves etching a trench at least partially through the silicon substrate and, possibly, the overlying dielectric layers, and then depositing copper in the trench. This method, however, requires a hard mask and etch module capability. Furthermore, due to the topography of the wafer, a copper residue may remain over the surface of the wafer.
As a result, there is a need for a more efficient method and system of forming TSVs.